Rock-drill



(No Model.)

W. H. RANDALL.

ROCK DRILL.

Patented July 24 DINVENTDEL fiwwr.

N. PETERS. mwum w. WM. D. C-

UNITED STATES PATENT OFFICE.

VILLIAM H. RANDALL, OF SAN FRANCISCO, CALIFORNIA.

ROCK-DRILL.

SPECIFICATION forming part of Letters Patent No. 281,922, dated. July24, 1 883.

Application filed February 21, 1883.

To a, whom it may concern:

Be it known that I, WVILLIAM II. RAN- DALL, a citizen of the UnitedStates, residing at San Francisco, in the county of San Fran- 5 cisco,State of California, have invented a new and useful Improvement inRock-Drills, of which the following is a full, clear, and exactdescription, reference being had to the annexed drawings, making a partof this specification, in whiel Figure 1 is a perspective view of myimproved rock-drill. Figs. 2 and 3 are side views, showing the drill indifferent positions. Figs. 4 and 5 are detail views of the bit andshank.

Similar letters indicate like parts throughout the several views.

The object of this invention is-to provide an improved means forenlarging the diameter of a drill-hole at the bottom thereof, and it isintended as an improvement upon that class of rock-drills for whichLetters Patent of the United States were granted to Edward J. Williams,August 20, 1879.

Referring to the drawings, a represents the cutting-bit, which isprovided with a curved dog or cuttingedge, slightly contracted orrounded at both corners to avoid slipping off at these two points whenin operation. The upper end of the cutting-bit is provided with a tenon,c, which fits into a recess, b, in the end of the drill-stock c. Acrescent-shaped .recess, d d, is formed 011 both sides of the ten- 011,and square shoulders e e are made in the front and back portion thereof.The shoulder represented at extends alittle farther downward or outwardtoward the end of the bit than that of the opposite shoulder,(represented at 0,) so as to give a forward inclination to the bit. Itis also beveled inwardly or downwardly to an acute angle, while theshoulder eis slightly depressed at its junction with the tenon, and isinclined or beveled upward or outwardly, so that when the parts areunited a close union will be had at that point with the shoulders uponthe drill-stock, to be hereinafter more fully described. The end of thedrill-stock is recessed to receive the tenon, as shown, and is providedwith the 50 beveled shoulders f f, to receive and fit the beveledshoulders of the drill-bit heretofore (No model.)

described. It is also provided with a knuckle or ears, 9 g, which arerounded to fit into the rounded recesses upon each side of the tenon,while a pin, 71-, passes through the knuckle and tenon, which unites andholds the parts together. By this construction, when the impact takesplace, the force of the blow will be received upon the shoulders c andf,at which point the union or the bit is close and strong, and theshoulders will not become battered down, neither will the tenon slipfrom its socket.-

WVhen the drill enters the drill-hole, the bit is on a line parallelwith the drill-stock, and in practice the drill-bit is always at aninward angle or incline of about thirty degrees, as shown in Fig. 3, andcuts outwardly as the drill-stock is rotated, thus quickly cutting out7c a chamber at the bottom of a drill-hole, while the impact or blow isalways received upon the beveled shoulder e of the bit and the beveledshoulder f of the stock when the two are united, and the side shouldersor knuckles are relieved from impact or concussion, and the force of theblow is distributed or conveyed more nearly to the center or axial lineof the drill-stock than in any other drill now constructed for the samepurpose as that of my invention.

The importance and value of my cuttingbit should not be lost sight of,as by the peculiar construction of its curved end I am enabled to cutthe chamber rapidly, and with a success that has heretofore beenunattained in the art of enlarging or chambering drill-holes at thetermination thereof.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, 9c is In a rockdrill, the combinati on of thedrillstock 0, having recess 1), beveled shoulders f f, and rounded ears9 g, the cutting-bit a, havinga tenon, a, crescent-shaped recesses d 95(l, and square shoulders e e, and the connecting-pin 71, substantiallyas described.

In testimony that I claim the foregoing I have hereunto set my hand andseal.

WILLIAM H. RANDALL. [L. s.]

\Vitnesses:

.C. W. M. SMITH, Gnlls. E. KELLY.

